Display screen portion with transitional user interface



FIG. 1 is a front view of the first image in the sequence for a transitional user interface for a portion of a display screen showing the new design; and,

FIG. 2 is a front view of the second image thereof.

The appearance of the transitional image sequentially transitions between images shown in FIGS. 1-2. The process or period in which one image transitions to another forms no part of the claimed designed. The broken line showing of a portion of a display screen, shapes and text is included for the purpose of illustrating environment and forms no part of the claimed design. 

The ornamental design for a display screen portion with transitional user interface, as shown and described. 